Specifically, the effects wheel assembly comprises a supporting device which rotates about a first axis; an effects wheel having a hub, which extends about a second axis, and an effects portion, which extends about the hub and is suitable to generate optical effects when intercepting the light beam; the supporting device and the effects wheel being selectively connectable to each other.
The definition “effects wheel” comprises, for the purposes of the present description, both an effects wheel having an effects portion defined by a metal annular plate suitable to accommodate gobos, and an effects wheel having an effects portion defined by a glass disc.
The term “gobo” defines a metal disc, typically made of stainless steel or glass, in which a motif or shape suitable to shape the light beam is obtained. Each gobo is generally coupled, in a releasable manner, in a respective seat of the metal annular plate.
Generally, the effects wheel is connected to the supporting device by a screw. This fastening mode does not allow the effects wheel to be easily coupled with the supporting device and compromises the interchangeability thereof.
In order to avoid this drawback, effects wheel assemblies of the above-described type, which include a magnetic fastening device between the effects wheel and the supporting device, have been developed. The mentioned effects wheel assemblies are, inter alia, disclosed by U.S. Pat. Nos. 6,971,770 B2 and 7,222,997 B2, which is the continuation in part of U.S. Pat. No. 6,971,770 B2.
In accordance with the aforementioned U.S. Pat. No. 6,971,770 B2, the connection between the supporting device and the effects wheel is obtained by means of a washer, which is defined by a permanent magnet, is fixed to the effects wheel, and is fastenable to the supporting device, which is made of ferromagnetic material.
In accordance with the aforesaid U.S. Pat. No. 7,222,997 B2, the connection between the supporting device and the effects wheel is obtained by means of a washer, which is defined by a permanent magnet, is fixed to the supporting device, and is fastenable to the effects wheel, which has a hub made of ferromagnetic material.
U.S. Pat. No. 7,222,997 B2 also includes the solution in which both the supporting device and the effects wheel comprise respective washers consisting of permanent magnets.
The clamping by means of magnetic force is not sufficient to ensure the correct alignment between the first axis of the supporting device and the second axis of the effects wheel. For this reason, the effects wheel assemblies defined above comprise respective centering means, each of which is defined by a hole and a pin which may be reciprocally coupled and respectively staggered with respect to the first and second axes so as to transmit a torque between the supporting device and the effects wheel.
The effects wheel assemblies identified above have proven to be effective; however, coupling the effects wheel with the supporting device is difficult because the space inside the light fixture is confined and does not allow the operator who couples the effects wheel with the supporting device to see the coupling area. Therefore, centering is made by trial and error in sequence, and also provided that the magnetic force inadvertently attracts the effects wheel when the operator approaches the hub to the effect wheel within a given distance.